init-system

init-system

Declarative startup/shutdown for your Node.js apps.

This solution has a dependency declarations similar to Linux startup systems or Makefiles. It also has inversion of control similar to middleware.

Usage

First we need to declare our services.

// services/my-service.js

module.exports = {

	// The name of this service.
	provides: 'myService',

	// The dependencies of this service.
	after: ['config', 'database'],

	/*
		Below is the startup and shutdown logic.

		services: object
			This object holds all of the dependencies
			declared in "after".

		provide: function(value) => Future
			A function you need to call to signal
			your service is created and ready for use.
	*/
	service: function*(services, provide) {

		// Use your dependencies.
		const myService = new MyService(services.config, services.database);

		// Let init-system know the service is ready.
		const exitCode = yield provide(myService);

		// Do our shutdown logic.
		myService.close();

		// Pass on the exit code.
		return exitCode;
	}

};

Then in our main script, load them using init-system.

// index.js

const init = require('init-system');

init.services(

	// Ordering is done in the service descriptions,
	// so we can simply provide an unsorted array.
	[
		require('./services/config.js'),
		require('./services/my-service.js'),
		require('./services/database.js')
	],

	// Node callback.
	function(err, exitCode){
		if(err){
			console.error(`Error during application startup / shutdown: ${err}`);
		} else {
			console.log(`Application exitted with ${exitCode}`);
		}
	}

);

Available options

You can call init.services(services, [options], callback) with an options object to change some behavior.

key	type	description
logger	function(message)	Allows you to set a logger for verbose startup / shutdown messages.

View example usage for the options

const options = {

	// Sets a logger for verbose startup / shutdown messages.
	logger: function(message) {
		console.log('init-system', message);
	}

};

init.services(
	[/* services */],
	options,
	function(err, exitCode) { /* callback */ }
);